It is noted that a characteristic phenomenon of the parturition of said large animals consists in holding the tail in raised position for a length of time that has been estimated at two seconds. A prior publication FR-2392599 of the present applicant showed a way, in which this phenomenon has been utilized to alert the cattle or horse raiser to the imminence of parturition, and described a detecting and warning system consisting of a sound alarm mechanism triggered by said phenomenon, wherein the warning is sounded only after an uninterrupted duration of the phenomenon, such duration being measured by an adjustable timer. This mechanism was contained in a box, which can be attached to the rear end of the back of the animal; the distal end of a flexible arm articulated on the box was fastened to the tail and followed its movements.
More recently, improvements have been made in this apparatus, which consist in the replacement of the timing and sounding mechanism with electronic means, each apparatus comprising a microswitch, a radio transmitter and a dry cell power supply; associated with one or more of the transmitters there is a receiver located on the farm where the herd is raised, the herd being free or held in a stable or barn or let out to graze.
This system, although it was satisfactory in operation, had the disadvantage of a relatively high cost because the transmitter in each individual apparatus had to be powerful enough to reach the receiver, particularly in the case of herds in pastures. Furthermore, among large herds, several females can drop young at the same time. This made it necessary, in practice, to provide the herd with a plurality of detectors, without which interest in the monitoring system was lost, also because, even if the herd was not very large, the cost became comparable to that of direct human surveillance.
Another disadvantage was that, since the timing means could be activated by tail movements other than the movement preceding parturition (for example the raising of the tail prior to urination), a large consumption of the electrical energy was required by the electronic timer and this involved very frequent replacement of the batteries. Furthermore, the continual analog radio signal of sufficiently great power to reach the remote receiver also required a great consumption of energy. Other disadvantages connected with the transmission power might result from regulations concerning the use of radio frequencies.